Three weeks ago, I wrote about the collapse of the Pacific cod population in central and southwestern Alaska. Over the course of two years, cod went from one of the most prolific fish species in the area to nearly non-existent. The Alaska Department of Fish and Game slashed commercial fishing quotas in 2017, but there were so few cod, commercial fishermen struggled even to catch the allowed poundage. The economic ramifications from the crash of the Pacific cod fishery are just beginning to affect Alaska’s ports, and biologists believe it will be years before the launch of another viable cod fishery.

This week, I’ll explain more about the history of the Pacific cod fishery and commercial methods for harvesting cod in Alaska. First, though, I want to emphasize the importance of Pacific cod not only to fishermen but also to consumers. Most of us at some point in our lives have eaten cod; whether it was a fish stick, a fish sandwich, fried fish, or baked white fish, cod is one of the most popular fish served by restaurants from fast-food drive-ins to diners to gourmet bistros. Cod has a mild flavor and a dense, flaky white flesh. It freezes well and can be shipped long distances. Cod liver oil is made from cod livers and is an important source of vitamin A, vitamin D, vitamin E, and omega-3-fatty acids.

The Pacific cod fishery gained traction just as the Atlantic cod fishery began to crash. The Atlantic cod fishery lasted for more than 1000 years and was popular even during the Viking period, around 800 AD. The fishery was vital to Europe, Canada, and the U.S., but this widespread popularity of Atlantic cod led to its downfall. Atlantic cod populations survived centuries of human strife, ranging from plagues to wars, only to be fished to the point of annihilation because the many countries that commercially fished cod couldn’t agree on regulations to protect this valuable resource. With Atlantic cod no longer available, fish buyers looked to the Pacific.

Pacific cod have been commercially fished on a small scale since the 19th century, but the modern commercial fishery began in the early 1960s with the Japanese longline fishery in the Bering Sea/ Aleutian Island (BSAI) region.  Between 1980 and 1989, a U.S. trawl fishery and several joint venture fisheries began in both the BSAI and the Gulf of Alaska (GOA) regions, and by 1989 the U.S. commercial cod fishery overtook the foreign fishery in both the BSAI and GOA regions.

Multiple methods are now used to harvest Pacific cod, including trawl, longline, pot, and jigging. Between 1991 and 1999, trawl gear accounted for 52% of the cod catch, longline gear took 37% of the harvest, and pot gear caught 11%. After 2000, however, longline fishing became the most productive means of landing cod. Between 2000 and 2006, longline gear accounted for 46% of the catch, trawl gear 37%, and pot gear 16%.

According to recent NOAA Fisheries Service surveys of Pacific cod stocks taken only a few years before the population collapsed, the cod stocks in Alaskan waters were stable and were not being over-fished. In 2010, NOAA estimated the BSAI stock at 1 million metric tons and the GOA stock at 0.4 million tons. Biologists have closely regulated the Pacific cod fishery and have erred on the side of caution by setting strict quotas to protect not only the cod fishery but also marine mammals such as Steller sea lions that depend on cod for food.

Researchers are now working diligently to discover what happened to the Pacific cod. Why did the cod population crash in Alaska? The leading theory is the crash was caused by warmer-than-normal ocean temperatures which in turn caused a reduction in the biomass of phytoplankton and zooplankton in the North Pacific. Juvenile cod, like most young fish, depend on zooplankton as a food source. Because of the reduction of zooplankton in the North Pacific, juvenile cod had little to eat, and many starved to death.

If the zooplankton biomass in the North Pacific has decreased to the point where cod can’t find enough to eat, we should all be concerned, not only for cod but for all animals in this portion of the sea. Marine animals from the smallest fish and birds to the largest whales depend on phytoplankton and zooplankton to survive.

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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. If you like audiobooks, check out her audiobook version of Murder Over Kodiak. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.